fix: resolve -Wdiscarded-qualifiers warnings in ifconfig_route and complete_config

fix: resolve -Wdiscarded-qualifiers warnings in ifconfig_route and complete_config

In ifconfig_route, remove const from the value parameter as it is
written through via sep (*sep++ = 0) and is only called from finalize_join()
with a mutable buffer.

In complete_config, change dot to const char* as it is only used for
pointer arithmetic and reading, never written through.

Signed-off-by: Rudi Heitbaum <rudi@heitbaum.com>